Total Nitrogen is an essential
nutrient for plants and animals.
However, an excess amount of
nitrogen in a waterway may lead to
low levels of dissolved oxygen and
negatively alter various plant life and
organisms. Sources of nitrogen
include: wastewater treatment
plants, runoff from fertilized lawns
and croplands, failing septic
systems, runoff from animal manure
and storage areas, and industrial
discharges that contain corrosion
inhibitors.

In 2018, Lohand have developed new product LH-D62 total nitrogen detection meter.It is small size,portable type,specially for outdoor use. Here is the photo: